feat: add antigravity-acp agent

[shubzkothekar]

Add Agent Client Protocol (ACP) server for Google Antigravity's agy CLI tool to the ACP registry with binary
distribution for all 6 platforms (darwin/linux/windows, aarch64/x86_64) at version 1.0.12. Uses the official Antigravity icon converted to 16x16 monochrome SVG with currentColor.

[Malix-Labs]

🛑 BE ADVISED 🛑

Google's ToS and FAQ is very clear that using is forbidden and might get you banned

https://antigravity.google/docs/faq#why-cant-i-use-third-party-software-eg-claude-code-openclaw-opencode-with-my-antigravity-login :

Why can’t I use third party software (e.g. Claude Code, OpenClaw, OpenCode) with my Antigravity login?

Using third party software, tools, or services to access Antigravity is a violation of our Terms of Service, and severely degrades the experience for legitimate product users. Such actions may be grounds for suspension or termination of your account. If you would like to use a third party coding agent with Gemini, we recommend using a Vertex or AI Studio API key.

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In zed-industries/zed#57221 (reply in thread), @shubzkothekar stated that it might not be detectable, but I maintain those claims cannot be verified since agy is closed-source

Also see shubzkothekar/antigravity-acp#3